差分法

It is shown that such a model can be used to design a nonlinear controller by techniques of norm H(subscript ∞) with the goal of maintaining relative equibalance water level along the open-channel reach.

以节制闸紧急启闭造成的水位波动和渠道物理建模的不确定性为抑制目标，采用泰勒级数和基于泛函估计有限差分法对Saint-Venant方程进行逼近形成了有限维状态方程，在H范数意义下对模型进行求解。

This one-way wave equation fits eikonal equation and transport equation corresponding to full acoustic wave equation in travel-time and first order amplitude. According to the perturbation theory often used in inverse solution, we split the velocity field into intraformational constant velocity background and variable velocity disturbance. Then we calculate time-shift quantity of migration and amplitude correction coefficients for wavefield depth continuation in total uniform formation and each formation.

基于反问题求解中常用的摄动理论，把速度场分裂为层内常速背景和变速扰动，求得整个均匀层波场深度延拓的偏移时移量及振幅校正系数、各层的偏移时移量及振幅校正系数，从而得到一个基于傅里叶有限差分法的双域保幅叠前深度偏移算子方程。

The multiresolution time-domain algorithm based on the scaling function of the Daubechies wavelet is introduced, and the perfectly matched layer absorbing boundary condition for the algorithm is deduced. In order to overcome the difficulties due to the nonlocalized property of the MRTD basis functions, the pure scattered-field formulation is adopted. The method presented is applied to the scattering analysis of multiple conducting objects, and the numerical results are compared with those by the traditional finite-difference time-domain method. It is shown that the computational resource is reduced drastically without sacrificing much accuracy.

对基于Daubechies小波尺度函数的时域多分辨分析算法进行了详细论述，推导了MRTD算法的完全匹配层吸收边界条件，为克服传统MRTD方法中基函数存在着非局部性的缺点，在源的加入上采用了纯散射场方法；并应用该算法对多目标的电磁散射特性进行了分析，数值结果表明，MRTD算法与传统的时域有限差分法结果相吻合，大大节约了计算资源。

However, it takes too much time and space for simulating a model with a relative large scale. A pseudospectral time domain method has the advantage of saving time and computer memory for the same simulation accuracy as that of FDTD.

通常采用的时域有限差分法在网格足够细的情况下能够精确地模拟井中雷达，但对于相对较大的模型，要得到较好的精度其所需要的时间和计算机内存都非常大。

In the last chapter of this paper, several remarks of this study were discussed. Considering saving the computer memory and increasing the calculation speed, the Pseudospectral time-domain numerical method is more effective than the FDTD method.

从节约计算机内存和提高计算速度方面考虑，电磁场数值计算建议采用时域伪谱算法来代替时域有限差分法，并进行了相应的比较和分析。

Combining the specific hydrogeological structure and related parameters, the pumpage and its composition were calculated by a three-dimensional finite difference method.

结合具体的水文地质结构及有关参数，采用地下水流三维有限差分法计算了各渗流井的出水量及其组成。

The modified Reynold＇s equations of first-order slip-flow and second-order slip-flow for the micro gas bearing are obtained.

利用有限差分法对连续流、一阶滑移流和二阶滑移流的雷诺方程分别求解，得出相应的承载力和偏位角。

Solving the Reynold＇s equations with the finite difference method, the gas pressure distributions of continuum flow regime and slip regime are obtained.

利用有限差分法对雷诺方程求解，得到两种情况下的气压分布，进而得到相应的承载能力和偏位角。

The use of stabilization methods for convenient mixed elements introduces stabilization parameter which results in the nonzero positive semidefinite lower right block.

论文中应用了两种离散鞍点问题的方法，一种是低阶混合协调有限元方法，另一种是M.A.C格式的有限差分法。

Energy deposition at the interface of the particles caused by micro-explosive welding in explosive consolidation of metal powders is analyzed by symmetrical impaction model of uncompressible liquid. Two-dimensional equation of energy in the flow field of explosive welding is deduced and solved by finite difference method. Then the distribution of the temperature in the flow field is calculated on the basis of considering the adiabatic compression.

摘 要：以不可压缩理想流体对称碰撞模型对金属粉末爆炸烧结中由微爆炸焊接引起的颗粒界面附近沉积的能量进行了分析，在考虑热传导效应的基础上推导出了焊接流场中二维形式的能量方程并用有限差分法对其进行了求解，在考虑冲击绝热压缩贡献的基础上计算出了焊接流场中的温度分布。

The split between the two groups can hardly be papered over.

这两个团体间的分歧难以掩饰。

This approach not only encourages a greater number of responses, but minimizes the likelihood of stale groupthink.

这种做法不仅鼓励了更多的反应，而且减少跟风的可能性。